This invention relates to an access control system and method, particular access control of a distributed system in which the resources of remote sites are shared using a computer network, by way of example.
Access control in a distributed system generally is achieved by combining an authentication mechanism in the distributed system with a resource protection mechanism at each site. For example, a distributed file system, which is a means of sharing files via a network, is used in a comparatively small-scale network environment such as a local area network (LAN). In such case user authentication means at the site level is appropriated in the network environment as well by unifying modes of user management, and resource protection is achieved based upon the authority granted to authenticated users. The file access control means for implementing this generally is provided by the operating system (OS).
In a comparatively large-scale network such as a wide-area network (WAN), on the other hand, use is made of authentication by an authentication system because unifying modes of user management is difficult. In a large-scale network environment, opportunities to share resources per se are fewer than in a small-scale network. However, in terms of providing the mechanism eventually used as the resource protection mechanism, the situation is the same as in the case of the small-scale network environment.
However, the following problems arise in the art described above:
The first problem is that satisfactory reliability cannot be assured merely by applying the site-level user authentication mechanism to a distributed system. Even if modes of user management are unified between sites, no legal force is involved and a certain site is capable of individually altering some of the management information. In cases such as these, it is possible for a site administrator to impersonate a user and it is difficult for the resource provider to detect this.
The second problem is that in a scenario in which the resource protection mechanism provided by the operating system (OS) is applied to distributed resources, ordinarily this is effective only at the site at which the resource protection mechanism is operating. Consequently, if there is an externally applied request for operation of a resource, the request must be dealt with based upon the rightful authority given to the site. However, as long as users once authenticated possess the same authority, it is not possible to cope with a situation in which reliability or level of authorization differ depending upon the site, even for the same user.